You would first have to determine whether there are more users or devices (i.e. computers) and then purchase the appropriate number of user or device CALs.
Typically it would be based on number of actual users, but in situations where multiple users share a workstation (e.g. in shifts) it may actually be cheaper to license based on number of devices. Another option is to purchase a SQL Server processor license, but this is typically more expensive if you don’t have a large number of users.
According to Microsoft’s licensing structure, DocRecord actually requires at least 1 user or device CAL for each DocRecord user.
Refer to DocRecord Product Specifications (prismsupport.com) for details.